1. Field of the Invention
The present invention relates to a power saving control system and a power saving control method that are adapted to a system comprising a plurality of electric devices for which different response speeds are required. More particularly, the present invention is concerned with a power saving control system and a power saving control method that are adapted to a system comprising a plurality of data storage devices.
2. Description of the Related Art
Along with the recent rapid innovation of information communication technologies, the information society has rapidly advanced and the amount of information to be handled has greatly increased. As a result of the popularization of the Internet, the amount of information to be handled, especially online, has drastically increased. Accordingly, the number of data server systems is markedly increasing. Many data server systems are more or less required to handle data in real time while they are in operation.
Many data storage devices currently adapted to the data servers are magnetic disk drives. An increase in the number of magnetic disk drives, or more particularly, an increase in the number of data storage devices capable of handling data online in real time leads to an increase in a power consumption. Needless to say, an energy-saving technology for saving the energy consumed by an individual device is making progress, and more and more devices are being provided with a feature supporting a so-called power saving mode. However, the increase in the amount of data a current information society is required to handle is overwhelming the progress made by the energy saving technology. Moreover, a data storage device is frequently accessed due to an increase in the need for quick response. Therefore, an energy saving mode cannot be utilized fully effectively. Accordingly, the present invention is intended to provide a means for not only meeting a requirement for a fast response by an online data storage device but also to utilize an energy saving feature.
[Patent Document 1] Japanese Unexamined Patent Application Publication No. 2001-93220
[Patent Document 2] Japanese Unexamined Patent Application Publication No. 2000-215002
[Patent Document 3] Japanese Unexamined Patent Application Publication No. 11-73710
In general, a plurality of data storage devices is employed in the storage of a large amount of online real-time information. This is because one data storage device cannot meet a performance-related requirement. Many data items are allocated to the data storage devices and stored therein. At this time, the data items are often classified in terms of data management with no consideration taken into the properties thereof, or especially, the access frequencies or response times required therefor. The classifying method poses no problem as long as an amount of online real-time data is relatively small. However, when the number of data storage devices is increased due to an increase in an amount of data, a power consumption required for waiting data to be received or to be transferred expands enormously. The underlying problem of the classifying method has come to light from the viewpoint of environmental protection.
As one solution to the problem, a method for controlling data storage devices has been proposed in the Japanese Unexamined Patent Application Publication No. 2001-93220.
FIG. 11 is a block diagram showing the configuration of a data storage system disclosed in the foregoing patent publication. Referring to the drawing, the data storage system comprises a computer 110 and a HDD group 120 including first to fourth hard disk drives (HDD) serving as external data storage devices.
The computer 110 comprises an operating system (OS) 130, an idle time detecting means 140, and an input/output monitoring means 150.
The OS 130 comprises an input/output control means 131, a motor start/stop control means 132, and a cache control means 133.
The input/output control means 131 and cache control means 133 control transfer of data to or from the HDDs, which belong to the group 120 of HDDs, according to predefined access frequencies.
The motor start/stop control means 132 controls starting or stopping of a motor serving as an HDD driver.
The idle time detecting means 140 detects an idle time during which the group 120 of HDDs does not respond to an input signal.
The input/output monitoring means 150 monitors transfer of data from the OS 130 to the HDDs, and records the number of times, by which data is transferred to or from each HDD during a unit time, for each data at every time of measurement.
When the system shown in FIG. 11 is in operation, data whose access frequency is high is temporarily moved to an HDD whose access frequency is detected to be high by the input/output monitoring means 150. This is intended to create an HDD whose access frequency is low. Furthermore, a time during which the HDDs are not accessed at all is measured by the idle time detecting means 140. If the length of the time is equal to or larger than a predetermined value, the motor start/stop control means 132 extends control to completely stop a spindle motor associated with each HDD. Thus, unnecessary consumption of power by the HDDs is suppressed.
However, if data requires fast response though it is accessed less frequently, in this case, when only an access frequency is taken into consideration, as the data is stored in an HDD whose access frequency is low, a long time is required for starting the spindle motor. This poses a problem in that the data cannot be accessed quickly.
The invention described in the above patent publication takes only an access frequency into consideration. There is data whose access frequency is low but which is required to be accessed quickly. When the data is moved to and stored in an HDD whose spindle motor is not rotating, an action cannot be performed within a required response time. Moreover, it is hard to automatically identify a request for quick response through measurement performed by a data storage device. Even when the contents of the patent publication describing an access frequency are broadly interpreted, the problem cannot be solved.